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How do lun reset and target reset commands affect SCSI-2 Reservations?

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Applies to

  • Data ONTAP 8
  • ONTAP 9

Answer

Background

  • An initiator sets a reservation on a LUN in order to prevent another initiator from making changes to the LUN, similar to a 'file-locking' concept.
  • SCSI reservations are always set by a host initiator, and ideally, the same initiator performs a SCSI release on the LUN in use.
  • Most LUNs are mapped to a single host, but in the case of a host cluster (e.g. VMware, SQL, Oracle), the same LUNs are mapped to multiple host nodes.
  • In some cases, it might be necessary for the host to clear a reservation that it did not initiate.
  • This is performed by running the 'lun reset' and 'target reset' SCSI commands.

 

Do you have to use a specific LUN when running the 'target reset' command?

The 'target reset' command can be run by an initiator without addressing a specific LUN, but a 'lun reset' command requires a specific LUN to be addressed.

 

Will a SCSI 'lun reset' command clear a SCSI-2 reservation?

Yes

 

Can a SCSI 'lun reset' command be run from any initiator, on any host, that has visibility to the LUN?

Yes, but the 'lun reset' command needs to be addressed to a specific LUN.

 

Will a SCSI 'lun reset' command affect any other initiators that are logged into a specific LUN?

Yes, all initiators mapped to a specific LUN will receive a LUN RESET notification.

 

Will a SCSI ' target reset' command affect all LUNs, from all initiators, that are logged into a target LUN?

The 'target reset' command on a NetApp SCSI target resets only those LUNs that are mapped to the initiator that is running.

 

Will a SCSI 'target reset' command clear SCSI-2 reservations on a mapped LUN that resides on a target?

Yes (see previous question). A SCSI-2 reservation will be cleared only on those LUNs that are reset.

 

Will a 'lun reset' or 'target reset' command affect SCSI-3 reservations?

No

 

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